Currently, at least three (3) types of rings are typically utilized to perform the required sealing and oil scraping functions associated with the reciprocal operation of a piston in a combustion cylinder of an IC engine. These three types of piston rings are often respectively referred to as the compression ring, typically located adjacent the end of a piston closest to the combustion chamber; the oil control ring, typically located adjacent to the end of a piston closest to the crank case; and one or more intermediate rings, typically located at one or more intermediate positions between the compression and oil control rings. In operation, the compression ring serves to form at least a partially sealed condition around the piston in cooperation with an oil film present on the cylinder wall, for maintaining a pressure differential condition between the combustion chamber and the crank case during the reciprocal movement of the piston in the combustion cylinder. This is most important during the compression stroke and power stroke of the piston when the combustion chamber is highly pressurized relative to the crank case. The oil control ring serves to scrape or wipe oil present on the cylinder wall to more uniformly distribute the oil and maintain an even oil film on the wall for lubrication and sealing purposes, mostly during the intake and power strokes of the piston when it is moving towards the crank case, the oil control ring floating or gliding over the oil film on the cylinder wall during the compression and exhaust strokes when the piston is moving in the opposite direction. The intermediate ring or rings typically supplement the sealing and oil scraping functions of the compression ring and oil control ring.
Importantly, the compression, intermediate, and oil control rings are typically of a gapped or split construction, that is, they are not circumferentially continuous. One advantage of this construction is that it facilitates passage of the rings over the outer surface of the piston to allow installation of the rings in circumferentially extending grooves in the outer surface. However, the gapped or split construction of the rings also contributes to at least two well known problems. One problem is known as "blowby" which is characterized by the escape of pressurized combustion gases from the combustion chamber past the piston rings to the crank case and beyond. Blowby is believed to occur mostly through the gaps or splits in the piston rings or between the ring and groove and is a contributing cause of combustion chamber compression and efficiency losses, crank case oil contamination, and pollution output. The second problem is the leakage of crank case oil in the opposite direction through the gaps or splits in the rings to the combustion chamber, which leakage has been found to result in increased oil consumption, particulate emissions and deposits which cause pollution and other problems.
Known alternatives to gapped and split piston rings include a variety of circumferentially continuous piston ring constructions, and constructions having abutting and/or interlocking circumferential end portions, all of which alternative constructions have been observed to achieve only limited improvements with regard to the above-discussed problems. See, for instance, Melchior, U.S. Pat. No. 4,794,848, issued Jan. 3, 1989; Hinshaw et al. U.S. Pat. No. 5,398,945, issued Mar. 21, 1995; and Martial, FR 2 702 024.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.